The chart is crap for many reasons. It even uses the stupid Mercator projection.

The USA does have cheap housing relative to income, especially outside the big coastal markets and a few other hotspots like Denver and Austin.

For example, incomes are about 4 times higher in suburban Ohio compared to Slovakia, but the housing is somewhat more expensive in Slovakia.

Europe has high costs because cars and gas are expensive so people don’t want to live far from work and drive. Europe also generally refuses to change the ag zoning right outside of its cities. My summer working in Europe, I lived at the very edge of where development was allowed. There was an 8-floor apartment tower and a bunch of townhouses or large expensive homes on small lots on one side of the zoning line, then cow pastures and forest on the other. It was charming, but increased housing costs. You generally won’t ever see in California a cow so close to an apartment tower you could hear it moo and toss it half your pain au chocolat, which I did.

Eastern Europe also suffered from little and low quality housing development during the communist era.